If you haven't heard of the hilarious JibJab parody of "This Land is Your Land," starring George W. Bush and John Kerry, click on that link, then come back here when you're done laughing. I'll see you in an hour or two.

Well, the supposed owners of the copyright on the original song weren't amused, so they threatened a lawsuit. But the good guys struck back. Not only is parody permissible (are they gonna sue Weird Al Yankovic next?), but the good guys made a convincing case that "This Land is Your Land" is public domain!

This was a case of a publisher trying to stack the deck in its favor to eke out a few extra years of copyright, trying to save 20 bucks, or both. The song was first published in 1945, but the publisher prefers to stick with a 1956 copyright, renewed in 1984.

JibJab's goal was to protect its own skin, so the publisher is sticking by its 1956 copyright. Someone else will probably have to fight that battle.

Sadly, the way copyright law is now, it's almost impossible for something to fall into the public domain except by accident, as in this case. But at least we have a demonstrable case of it happening once.